Power fastening tools include various driving mechanisms. One fastening tool includes a solenoid actuator that drives a blade which drives a fastener. Another fastening tool includes a motor-driven gearbox with an eccentric drive which lifts a plunger against a spring, then releases the plunger, with the spring driving the plunger and attached blade which drives the fastener. Another fastening tool includes a motor-driven gearbox that drives a linkage to compress air in a cylinder. The compressed air is then released into a smaller cylinder, driving a blade which drives a fastener. Another fastening tool includes a battery to power a device which ignites an air-fuel mixture, from which a rapid expansion within a cylinder drives a plunger and attached blade which drives the fastener.